Tubular electrode support for ceramic discharge lamp

ABSTRACT

An improved electrode support element for ceramic discharge lamps formed from the exhaust and fill tubulation extending through one or both of the arc tube refractory metal end caps. A section of the tubulation adjacent to but spaced from the inwardly extending end is notched out and that portion between the notch and the end is collapsed against the opposite side wall to form a double walled, U-shaped electrode rod gripping portion with improved centering and holding capabilities.

United States Patent 11 1 Knochel et al. 1 May 6, 1975 [54] TUBULAR ELECTRODE SUPPORT FOR 3,363,134 1/1968 Johnson 313/317 X CERAMIC DISCHARGE LAMP 3,497,756 2/1970 Knochel et al 313/331 [75] Inventors: William J. Knochel, West Orange; 1

Leo f' Cedar (Prove, bcfth Primary Examiner-Siegfried H. Grimm N g 'l Francis Flushmg, Attorney, Agent, or FirmB. R. Studebaker [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa. [57] ABSTRACT [22] Filed: Mar. 4, 1974 [21] Appl No 447 619 An improved electrode support element for ceramic discharge lamps formed from the exhaust and fill tubulation extending through one or both of the arc tube refractory metal end caps. A section of the tubulation 313/356 adjacent to but spaced from the inwardly extending [51] Int. Cl Hillj 1/94; l-lOlj 61/06 end is notched out and that portion between the notch Field of Search... 313/217, 2 220, 227429, and the end is collapsed against the opposite side wall 356 to form a double walled, U-shaped electrode rod gripping portion with improved centering and holding ca- [56] References Cited pabilities. 1

UNITED STATES PATENTS 2,508,114 5/1950 Jenne, Jr 313/331 X 9 Claims, 5 Drawing Figures J 36 I .9 5 o 'z PMENIEBIIAY 3,882,344

FIG. 3.

TUBULAR ELECTRODE SUPPORT FOR CERAMIC DISCHARGE LAMP BACKGROUND OF THE INVENTION This invention relates to high pressure ceramic discharge lamps and more particularly to an improved electrode support element formed from the exhaust and fill tubulation which provides improved centering and holding of the discharge sustaining electrode.

In discharge lamps employing the ceramic arc tube,

the opposed discharge sustaining electrodes are mounted at least at one end of the arc tube to the exhaust and fill tubulation which extends through the end cap or end closure of the arc tube body. Many such lamps employ refractory metal tubulation as the electrode support in both ends of the lamp and it should be understood that the improved tubulation design of this invention may be employed at both ends in such a lamp. Exhaust and fill tubulation is universally employed in the ceramic discharge lamp at least at one end of the arc tube to facilitate exhausting of the arc tube and filling with the discharge sustaining fill such as, for example, an amalgam of sodium and mercury. In the final step of arc tube fabrication the exhaust and fill tubulation is pinched off and sealed. Many tubulation configurations are available in the prior art and each is characterized by one or more deficiencies such as expense of manufacturer, nonrigidity of electrode support, or the inability to center the electrode with respect to the longitudinal axis of the are tube body. One example of a more expensive tubulation construction is illustrated in US. Pat. No. 3,243,635 in which the entire internal end of the tubulation is crimped down about the electrode rod or shank prior to welding and one or more apertures are required to be drilled in the tubulation body to provide for the exhaust and fill functions, after assembly of the electrode to the tubulation. U.S. Pat. No. 3,746,907 discloses another type of tubulation electrode support wherein all but a narrow strip of the tubulation is cut away on the interior end leaving a flexible strap which, through a pair of fingers at the end of the strap, grips the electrode rod or shank. This latter configuration not only requires more difficult fabricating procedures but provides a less rigid support for the electrode than the improved design of this invention.

SUMMARY OF THE INVENTION The novel improved tubulation design of this invention provides for rigid electrode support and almost perfect centering of the electrode with respect to the tubulation and arc tube longitudinal axes while requiring only minimal fabricating steps. The foregoing is accomplished in accordance with the present invention by providing in a ceramic discharge lamp which conventionally includes a base, an outer envelope sealed to the base, and a ceramic arc tube mounted within the outer envelope and electrically connected to the base, with the arc tube having refractory metal end caps or closures sealing off the ends thereof and carrying internally the discharge sustaining electrode, the improved electrode mounting and support element, at least at one end of the arc tube which comprises a length of the exhaust and fill tubulation of this invention sealed through an aperture in one end cap. This tubulation has a notched out section on the portion thereof extending inwardly of the end cap with that portion of said tubulation between the notched out portion and the inwardly extending end of the tubulation being collapsed from a convex-concave form to a concave-convex form to form a double walled electrode holding portion with its opposite wall portion. More particularly the collapsed wall portion extends substantially curvilinearly with and adjacent to the inner surface of its opposite wall portion to thereby form a double walled electrode holding portion with the notched out portion providing adequate access to the interior of the arc tube to accommodate the exhaust and fill functions.

BRIEF DESCRIPTION OF THE DRAWING Many of the attendant advantages of the present invention will become more readily apparent and better understood as the following detailed description is considered in connection with the accompanying drawings, in which:

FIG. 1 is a side elevational view partly in section of a ceramic discharge lamp employing the improved electrode support element of this invention;

FIG. 2 is an enlarged side elevation, partly in section, of an arc tube of the ceramic type employing this invention;

FIG. 3 is a side elevational view illustrating the tubulation after notching;

FIG. 4 is a side elevational view similar to FIG. 3 illustrating the tubulation after the end is collapsed; and

FIG. 5 is an end view of the collapsed tubulation of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to the drawings wherein like reference characters represent like parts throughout the several views there is illustrated in FIG. 1 a typical high pressure sodium lamp of the ceramic arc tube type generally designated 10. The discharge lamp 10 includes an outer envelope 12 of glass attached to a standard metal mogul base 14. A pair of lead-in conductors 16 and I8 (partially superimposed in FIG. 1) are conventionally connected to the mogul base 14 and extend through a re-entrant stem press 20 at the base of the envelope 12 in a conventional manner. Mounted on the upper end of lead-in conductor 18 is the arc tube support frame 22 which serves both to retain and mount the arc tube within the outer envelope 12 as well as to conduct electricity to the upper electrode of the arc tube. The frame 22 is supported at its upper end within the envelope 12 by a pair of resilient spring members 24 which serve to retain the frame 22 in a central location within the outer envelope 12 through resilient contact with the inner surface of the outer envelope.

A conventional ceramic arc tube 26 preferably of polycrystalline alumina or sapphire is mounted at its lower end to lead-in conductor 16 by means of a flexible wire 31 which encircles the exhaust and fill tubulation 30 of the arc tube and is welded to the lead-in conductor 16 in a manner disclosed in copending application Ser. No. 392,692, filed Aug. 29, 1973 for an Improved Ceramic Arc Lamp Construction" and owned by the assignee of this application. The tubulation 30 extends through an end cap 32 at the lower end of the lamp, which tubulation serves to mount the lower electrode 34 in accordance with this invention.

At the other end of the arc tube 26 is a nontubulation carrying end cap or end closure 36. An inverted T- 3 shaped lead-in conductor 38, including flange portions 39 is spot welded to the outside of the end cap 36 to provide electrical current to the electrode 40 mounted on the inner side of the end cap 36 by an electrode support element which is disclosed in detail in copending 5 application Ser. No. 447,618 filed the same date as this application for Electrode Support Element For Ceramic Discharge Lamp by the inventors of this application and owned by the same assignee as this application. The lead-in conductor 38 is electrically connected to the support frame by a flexible strap 42 at 44. The strap 42 is welded to the lead-in conductor 38 and to the lateral support bar 46 at their juncture. The lateral support bar 46 has channels therethrough at 48 which surround the vertical arms of the support frame 22 to provide for centering of the upper end of the arc tube with respect to the frame but in a manner which will permit longitudinal movement or expansion of the arc tube through the loose sliding fit relationship between the support frame 22 and the channels or apertures 48 in support bar 46.

As previously pointed out the exhaust and fill tubulation 30 extends through the end cap 32 and is brazed thereto along with lead-in conductor 31 by means of a niobium or titanium brazing ring in a manner disclosed in the aforementioned copending application Ser. No. 392,692 for An Improved Ceramic Arc Lamp Construction. As best illustrated in FIGS. 3, 4 and 5, a notch 50 is cut from the tubulation adjacent to but spaced from one end thereof. The portion 52 of the tubulation side wall which extends between the notched out portion and the adjacent end is then folded or collapsed against its opposite wall 54 as best seen in FIG. 5 to form a substantially U-shaped double walled electrode gripping portion. This double walled configuration produces a U-shaped cavity having a radius which approximates the radius of the cylindrical rod or shank portion 56 of the electrode 34 and provides for improved mechanical holding ability as well as better surface area and wall thickness and hence improved welding capabilities. As will be apparent the improved tubulation design of this invention can be employed at both ends of the arc tube 26 if desired as opposed to the nontubulation electrode mount illustrated at the other end of the arc tube in FIG. 2.

The exhaust and fill tubulation of this invention may be constructed of tantalum or niobium with niobium being preferred because of its compatability with the niobium end cap 32. The tubulation 30 is preferably /8 inch O.D. niobium tubing of approximately 1%1 inches in length. The area 52 between the notch 50 and the end of the tubulation is approximately 42 inch in length with the notch extending for a distance of about 1/10 of an inch along the tubulation length and to a depth which is slightly less than half the circumference of the tubulation. The depth of the notch is such that when the portion 52 of the tubulation is collapsed against its opposite side wall 54 the edge of the notch and the edge provided by the bend between the sections 52 and 54 will be substantially linear. After fabrication of the tubulation it is then brazed to the end cap 32 in a manner previously described and the electrode shank 56 carrying electrode 34 is then welded to the U-shaped rod gripping portion 52-54 of the tubulation.

As will be apparent from the foregoing, a large aperture is provided by the notch 50 to accommodate exhausting of the arc tube body and the filling with the discharge sustaining fill 58. After the exhaust and fill operations, the tubulation 30 is then tipped off and sealed as illustrated in phantom at 60. The double walled, U-shaped electrode gripping portion provides rigid mechanical support for the electrode as well as improved centering of the electrode with respect to the longitudinal axis of the arc tube. Fabrication of the tubulation involves only the relatively simple notching and collapsing steps.

What is claimed is:

1. In a ceramic discharge lamp including a base, an outer envelope sealed to said base and a ceramic arc tube mounted within said outer envelope and electrically connected to said base, said ceramic arc tube including refractory metal end caps sealing off the ends thereof and carrying internally thereof discharge sustaining electrodes, the improvement comprising:

an improved electrode mounting and support element at at least one end of said arc tube comprising a length of exhaust and fill tubulation sealed through an aperture in said cap, said tubulation having a notched out section on the portion thereof extending inwardly of said end cap with that portion of said tubulation between the notched out portion and the inwardly extending end of said tubulation being collapsed from a convex-concave form to a concave-convex form to form a double walled substantially U-shaped electrode holding and centering portion with its opposite side wall.

2. A ceramic discharge lamp according to claim 1 wherein said exhaust and fill tubulation is tantalum.

3. A ceramic discharge lamp according to claim 1 30 wherein said exhaust and fill tubulation is niobium.

4. An improved refractory metal exhaust and fill tubulation for a ceramic discharge lamp, said tubulation comprising:

an elongated, thin walled tubular member having a notched out portion adjacent one end thereof and a collapsed wall portion extending from said notched out portion to said adjacent end, said collapsed wall portion extending substantially curvilinearly with and adjacent to the inner surface of its 40 opposite wall portion to thereby form a double walled electrode holding portion.

5. The improved refractory metal exhaust and fill tubulation of claim 4 wherein said refractory metal exhaust and fill tubulation is tantalum.

6. The improved refractory metal exhaust and fill tubulation of claim 4 wherein said refractory m'etal exhaust and fill tubulation is niobium.

7. In a ceramic discharge lamp including a base, an outer envelope sealed to said base and a ceramic arc tube within said outer envelope and electrically connected to said base, said ceramic arc tube including refractory metal end caps sealing off the ends thereof and carrying internally thereof discharge sustaining electrodes, the improvement comprising:

an improved electrode mounting and support element at at least one end of said are tube comprising a length of exhaust and fill tubulation extending through the end cap at said at least one end of said arc tube, said exhaust and fill tubulation having a section thereof, adjacent to but spaced from the inwardly extending end, notched out with the portion of said tubulation between said notched out portion and the inwardly extending end of said tubulation being collapsed against its opposite side wall to form a double walled U-shaped electrode rod gripping portion with said opposite side wall.

8. The ceramic discharge lamp of claim 7 wherein 65 said tubulation is tantalum.

9. The ceramic discharge lamp of claim 7 wherein said tubulation is niobium. 

1. In a ceramic discharge lamp including a base, an outer envelope sealed to said base and a ceramic arc tube mounted within said Outer envelope and electrically connected to said base, said ceramic arc tube including refractory metal end caps sealing off the ends thereof and carrying internally thereof discharge sustaining electrodes, the improvement comprising: an improved electrode mounting and support element at at least one end of said arc tube comprising a length of exhaust and fill tubulation sealed through an aperture in said cap, said tubulation having a notched out section on the portion thereof extending inwardly of said end cap with that portion of said tubulation between the notched out portion and the inwardly extending end of said tubulation being collapsed from a convex-concave form to a concave-convex form to form a double walled substantially U-shaped electrode holding and centering portion with its opposite side wall.
 2. A ceramic discharge lamp according to claim 1 wherein said exhaust and fill tubulation is tantalum.
 3. A ceramic discharge lamp according to claim 1 wherein said exhaust and fill tubulation is niobium.
 4. An improved refractory metal exhaust and fill tubulation for a ceramic discharge lamp, said tubulation comprising: an elongated, thin walled tubular member having a notched out portion adjacent one end thereof and a collapsed wall portion extending from said notched out portion to said adjacent end, said collapsed wall portion extending substantially curvilinearly with and adjacent to the inner surface of its opposite wall portion to thereby form a double walled electrode holding portion.
 5. The improved refractory metal exhaust and fill tubulation of claim 4 wherein said refractory metal exhaust and fill tubulation is tantalum.
 6. The improved refractory metal exhaust and fill tubulation of claim 4 wherein said refractory metal exhaust and fill tubulation is niobium.
 7. In a ceramic discharge lamp including a base, an outer envelope sealed to said base and a ceramic arc tube within said outer envelope and electrically connected to said base, said ceramic arc tube including refractory metal end caps sealing off the ends thereof and carrying internally thereof discharge sustaining electrodes, the improvement comprising: an improved electrode mounting and support element at at least one end of said arc tube comprising a length of exhaust and fill tubulation extending through the end cap at said at least one end of said arc tube, said exhaust and fill tubulation having a section thereof, adjacent to but spaced from the inwardly extending end, notched out with the portion of said tubulation between said notched out portion and the inwardly extending end of said tubulation being collapsed against its opposite side wall to form a double walled U-shaped electrode rod gripping portion with said opposite side wall.
 8. The ceramic discharge lamp of claim 7 wherein said tubulation is tantalum.
 9. The ceramic discharge lamp of claim 7 wherein said tubulation is niobium. 